1. Field of Invention
The present invention relates to a piezoelectric resonator, a piezoelectric oscillator including an oscillator circuit element to oscillate the piezoelectric resonator, and a portable telephone and an electronic device using a piezoelectric oscillator.
2. Description of Related Art
A related art piezoelectric oscillator disposed in a package can be used in a wide variety of devices, for example, in small information devices, such as a HDD (hard disk drive), a mobile computer, and an IC card, and mobile communication devices, such as a portable telephone, a mobile telephone, and a paging system.
The related art constructs a piezoelectric oscillator in such a manner that a piezoelectric resonator and an oscillator are first constructed in separate packages and then the package including the piezoelectric resonator is placed on the package including the oscillator, as disclosed in Japanese Unexamined Patent Application Publication No. 63-244905.
The technique disclosed above can reduce or avoid various problems which will occur if the piezoelectric resonator and the oscillator circuit element are disposed in the same package.
That is, if the piezoelectric resonator and the oscillator circuit element are both disposed in the same resin-molded package, gas produced during the curing process is adsorbed by the piezoelectric resonator and degradation in performance occurs.
The above problem can be reduced or avoided by disposing the piezoelectric resonator and the oscillator circuit element in separate packages and putting one of them on the other. Furthermore, this technique makes it possible to produce a piezoelectric oscillator in a small form.
In the related art, it is advantageous to reduce in size various devices using a piezoelectric oscillator. To provide this advantage, it is required to further reduce the size of the piezoelectric oscillator.
To address or achieve the above requirement in the piezoelectric oscillator produced by housing a piezoelectric resonator and an oscillator circuit element in separate packages and then putting one of them on the other, the related art provides a structure shown in FIGS. 23 and 24, as disclosed in Japanese Unexamined Patent Application Publication No. 2001-332932.
FIG. 24 is a cross-sectional view taken along Plane C—C of FIG. 23. As shown in FIGS. 23 and 24, a piezoelectric oscillator includes an oscillator 2 and a piezoelectric resonator 3 firmly placed on the oscillator 2.
In the piezoelectric resonator 3, a piezoelectric resonator 7 is disposed in an internal space S1 of a ceramic package 3a. Grooves 5 are formed on side faces of the ceramic package 3a and electrodes 6 connected to the piezoelectric resonator 7 are formed in the respective grooves 5. The upper end of the ceramic package 3a is closed with a lid 4 made of metal.
The oscillator 2 is produced by placing an oscillator circuit element 11 on a device mounting part of a lead frame 13 and molding them with a resin 14. Of a plurality of leads 13a and 13b of the lead frame 13, leads 13a are bent downward such that they serve as external connection terminals used to mount the oscillator 2. The other leads 13b are bent upward and connected to the electrodes 6 formed in the grooves 5 of the piezoelectric resonator 3.
As described above, by using the lead frame 13 of the oscillator 2 in conjunction with the structure including the grooves 5 of the piezoelectric resonator 3, the electrodes 6 of the piezoelectric resonator 3 are electrically connected to the leads 13a of the oscillator 2 in a highly reliable fashion. Furthermore, this structure also allows components to be easily positioned.